Dual‐Phase Manganese Oxide/ZnO Nanocomposites for High‐Performance Supercapacitor via Synergistic Redox Enhancement

Abstract The integration of dual‐phase manganese oxides (MnO 2 ‐Mn 3 O 4 ) with zinc oxide (ZnO) nanocomposites presents a compelling strategy to advance supercapacitor electrodes by synergizing the redox activity with structural stability. Here, solvothermally synthesized MnO 2 ‐Mn 3 O 4 /ZnO nanocomposites (1:1, 1:2, 2:1 by wt%) are systematically investigated for their structural, optical, and electrochemical properties. X‐ray diffraction (XRD) confirms the coexistence of tetragonal Mn 3 O 4 and MnO 2 phases alongside the hexagonal ZnO phase, whereas FTIR and EDX validate the interfacial bonding and stoichiometric purity. Scanning electron microscopy (SEM) reveals spherical and agglomerated morphologies, and XRD computes reduced crystallite sizes (14.3 nm for the 2:1 composite), enhancing the surface area for charge storage. Optical analyses unveil bandgap modulation (2.16–3.95 eV) driven by type‐II heterojunction formation, suppressing recombination, whereas photoluminescence (PL) spectra highlight defect‐mediated transitions critical for charge carrier dynamics. Electrochemically, the MnO 2 ‐Mn 3 O 4 /ZnO (2:1) nanocomposite achieves a specific capacitance of 967 F/g at a current density of 1.5 A/g, an energy density of 108.8 Wh/kg, and a low charge‐transfer resistance of 377.4 Ω, outperforming individual MnO 2 ‐Mn 3 O 4 and ZnO components. A symmetric supercapacitor device delivers 39 Wh/kg energy density with 99.7% capacitance retention over 50 cycles, attributed to Mn 3+ /Mn 4+ redox synergies and the conductive framework of ZnO. This work establishes dual‐phase MnO 2 ‐Mn 3 O 4 /ZnO as a scalable and high‐performance electrode material, bridging redox‐driven energy storage with structural resilience for next‐generation supercapacitors.